Process of treating lead-bearing material



Patented Dec. 9, 1930 UNITED STATES PATENT OFFICE aLExaNnEa s'rswaa'r,or ROSELLE, NEW JERSEY, ASSIGNOB. T 0. ,L. CONSTANT- comr'amr, ornonoxsn, NEW JEasEY, A conroaarron or NEW JERSEY PROCESS OF TREATTN GLEAD-BEABIN G MATERIAL No Drawing.

. It has for its object to convert such material to substantiallychemically pure sulfate of lead.

I As generally obtained, ordinary waste battery paste, as a specificmaterial by way of n example and to which the invention is particularlyapplicable, comprises princi ally lead peroxide (PbO lead sulfate.(Pb Oand small amounts of antimony, usually .5% to 3% together with foreignorganic matter such as .wood and'rubber, as well as small amounts-ofiron, arsenic, etc. This paste material may be obtained in any suitablemanner from the scra battery plates, the same being separated rom saidplates and then .treated in bulk as hereinafter set forth. Or, otherloxidesoflead or mixtures of'the lead and lead oxides obtained fromdifferent sources may be similarly treated for conversion into pure leadsulfate.

Ifthe material to be treated comprises metalliclead and paste as, forexample, in the case of lead-battery plates, the plate portion may beseparated from the paste by any well known or special manner, forexample, as set forth in the 118. Letters Patent to Zuckermann No.1,587,623. Thereupon the aste material may be converted to sulfate hyfusion with an acid salt of an alkali metal asnitre cake, for example,as more particularly set forth in my D. S. Patent No. 1,610,899. a Or,the-plate with grid may be fused as a whole with sodium chloride, asmore particularly set forthin my United States Letters Patent. No.1,627,351, and whereby the oxides of-the' lead are convertedsubstantially'to lead chloride, the lead sulfate of thepaste-portionremaining as such, and the molten metallic lead beingsuitably removed therefrom. This mixture 'of chloride and sulfate isthen to be fused-with nitre cake or other suitable acid sulfate of analkali metah tebnvert the mixture solelyinto sulfate saay impuritiespresent in the separated portioni Application filed March 22, 19?.Serial No. 177,463.

- The sulfate thus obtained is to be purified as hereinafter set forth;but it has been found advantageous to obtain the sulfate from the gridmaterial by a different process and whereby a very substantial portionof the impurities such as antimony and arsenic, etc., are removed in theearly stage of the treatment so that the lead sulfate is more" readilypurified in the subsequent stages of the process. v

For example, in the case of the paste material which consistssubstantially of lead peroxide and lead sulfate with the small amountsof impurities, the same is to be treated with a solution of sulfuricacid and any soluble chloride which will form a soluble sulfate. A mostsuitable chloride for this purpose, especially due toits low expense andready availability,is sodium chloride or common salt. By this treatmentof the paste material with the aforesaid solvent .mixture, it has. beenfound possibleto complete-the reaction of sulfuric acid on peroxide oflead and which reaction is only partially;

completed by the usual treatment solely wit sulfuric acid. The reactioninvolved in the novel treatment is based upon the action of the chlorineof the chloride and one availableoxygen from the peroxide of lead in anacid solution, for example,

The treatment with the aforesaid solution, furthermore, involves aconversion into soluble sulfates of all other metals, such as tin,antimony, bismuth, zinc, copper, iron,

arsenic, -etc., and which are present'in more or less percentages asimpurities,

In carrying out this ,novetreaction, the

following procedure has been found to give satisfactory results:

Toone ton of, for example, dry, battery paste, there is added from600400 lbs. of salt and 100 gals. of water, the whole being thoroughlymixed; whereupon there is added slowly about 1,000 lbs. of sulfuric acidof a specific gravity of 1.84, while effecting a thorough agitationofthe mass.

This mixture is then slowly heated with I agitation of the mass until.all of the lead peroxide, and any other oxides of the paste, have beenconverted to sulfateprobably according to the following reactions:

OI PbO 211580, 2NaCl The temperature is thereupon increased until strongfumes of sulfuric anhydride (S are evolved.

By the heating process under these condi- 5 tions, approximately 80-85%of the antimony and arsenic present as impurities in the originalmaterial are removed as volatile chloridesSbCl and ASCIB.

After the entire mass has been. allowed to cool, it is to be treatedwith a solution of a. sulfate or acid sulfate, for example, sodiumsulfate or sodium acid sulfate, or other soluble sulfate of an alkalimetal, which is added thereto. The mixture is then again heated andagitated, the liquid removedin any suitable manner as by decantation orfiltering, and the residue washed free from impurities with water orwater containing a small amount of dissolved nitre cake,

the final washings being solely with water.

The resulting lead sulfate, which has thus been freed from the majorportion of the impurities,-or more or less impure lead sulfatesotherwise obtained, may be brought to an extremely pure condition by thefollowing treatment, to wit: subjecting the lead sulfate to treatmentwith a sulfuric acid solution'containing sodium sulfate; or, sodium acidsulfate alone may beiused, as well as solely sulfuric acid solution. Inthe latter instance, the necessary concentration of SO ions may beobtained by the utilization of suitably concentrated sulfuric acid, theoh- 5 ject being to prevent hydrolysis of base metals and keep the samein solution. The specific gravity of the acid, however, wouldnecessarily be extremely high, approximately 1.41, and would renderworhng therewith diificult as well as seriously attacking the utensilsemployed.

It is preferred, therefore, to make use of a comparatively weak sulfuricacid solution to which has been added sodium sulfate, or,

as aforesaid, to use merely a sodium acid sulfate solution, or both. Theacidity of these solutions should not be less than 2% free acid and thespecific gravity thereof 1.124 when making use of the sodium acidsulsofate;' and not below 1.189 when using the sulfuric acid solution andsodium sulfate. With these comparatively weakly acid solutions, it isnecessary, however, that the same be kept very hot as by passing steamtherethrough.

When a solution is employed containing from 540% of free sulfuric acidwith enough sodium sulfate or acid sulfate added thereto to bring thespecific gravity up to 1.219, the solution merely needs to be warm, forexample, having a temperature of approximately 50 C to 60 0.

Under the foregoing conditions, the antimony, tin, bismuth and othermetals forming soluble sulfates will be removed from the sulfate of leadand will also be prevented from hydrolizing so that the same may bereadily washed out from the lead sulfate which is recoveredsubstantially in a chemi-, cally pure state. After removal of thesulfate solution, the residue is to be thoroughly washed with water anddried. It will be understood, of course, that the percentages ofimpurities present will more or less govern the specific gravities ofthe sulfuric acid and sulfate solutions; but it has. been found thatwith impurities ranging from 03%, the minimum percentage of the freesulfuric acid is 2%, and that the specific gravity of the combinedsolutions should not be less than 1.124.

I claim:

1. The treatment of waste lead-battery paste which comprises thoroughlymixing one of sodium chloride in gals. of water and adding thereto 1,000lbs. of sulfuric acid of a specific gravity of 1.84, heating andagitating the mixture, then increasing the temperature; thereof untilstrong fumes of sulfuric anhydride are evolved and until substantiallyall lead oxides have been converted to an insol-' uble sulfate, allowingthe mixtureto cool, treat-ing the same with a 20% solution of a solublesulfate of an alkali metal, again heat-( ing and agitating the mixture,removing the liquid, and washing the residue with water.

3. The treatment of waste lead-battery paste which comprises thoroughlymixing one ton of the paste with a solution of 600700 lbs. of sodiumchloride in 100 als. of water and adding thereto 1,000 lbs. of sulfuricacid of a specific gravity of1.84, heatin and agitating the mixture,then increasing t e temperature thereof until strong fumes of sulfuricanhydride are evolved and until substantially all lead oxides have beenconverted to an insoluble sulfate, allowing the mixture to cool,

hydrolysis of soluble sulfates, removing the v liquid, and washing theresidue with water.

4 The treatment of lead bearing material which comprises subjecting thesame to a mixture of sulfuric acid and a soluble chloride capable offorming a soluble sulfate, and heating and agitating the mixture untilsubstantially all lead oxides have been converted to an insolublesulfate.

5. The treatment of lead bearing material which comprises subjecting thesame to a mixture of'sulfuric acid and a soluble chloride capable offorming a soluble sulfate, heating and agitating the mixture and thenincreasing the temperature until strong fumes of sulfuric anhydride areevolved and until substantially all lead oxides have been converted toan insoluble sulfate.

6., The treatment of lead bearing material which comprises subjectingthe same to a mixture of sulfuric acid and a soluble chloride capable offorming a soluble sulfate, heating and agitating the mixture, thenincreasing the temperature until strong fumes of sulfuric Y anhydrideare evolved and until substantially all lead oxides have been convertedto an insoluble sulfate, cooling the mixture, treating the same with asolution of a soluble sulfate of an alkali metal, removing the liquid,and washing the residue free from impurities.

7. The process of refining lead sulfate containing antimony, whichcomprises treating the same with a weak solution of sulfuric acid towhich a soluble sulfate of an alkali metal has been added to raisesufficiently the S0 ion concentration to prevent hydrolysis of solubleantimony sulfates.

8. The process of refining lead sulfate containing antimony, whichcomprises treating the same with a sulfate solution of free sulfuricacid content not substantially less than 2% and not substantiallyexceeding- 10% and to which has been added a soluble sulfate to raisesufiiciently the S0 ion concentration to prevent hydrolysis of antimonysulfate.

9. The process of refining lead sulfate containing antimony, whichcomprises treating the same with a solution containing substantially notless than 2% nor substantially more than 10% free sulfuric acid and analkali metal sulfate in an amount to raise sufficiently the S0 ionconcentrations to prevent hydrolysis of soluble sulfates.

10. The process of refining lead sulfate containing antimony, whichcomprises treating the same with a solution of a soluble sulfate of analkali metal having a specific gravity of substantially not less than1.124 and substantially not more than 1.219 and containing substantiallynot less than 2% nor substantially more than 10% of free sulfuric acid.

11. The process of refining lead sulfate containing antimony, whichcomprises treating

